Synthesis of [2]ferrocenophanes containing trivalent diphosphine units

Article abstract of DOI:10.1016/j.jorganchem.2012.04.022

Three (PR)₂-bridged [2]ferrocenophanes (R = ^tBu (10a), ⁿBu (10b), and Ph (10c)) in which the two C₅H ₄ rings of the ferrocene unit were bridged with a P(III) - P(III) bond were synthesized via Mg-mediated reductive coupling between the phosphorus centers of corresponding [Fe{C₅H₄P(Cl)R}₂]. The P(Cl)R groups of [Fe{C₅H₄P(Cl)R}₂] were derived from the P(NEt₂)₂ groups of [Fe{C ₅H₄P(NEt₂)₂}₂] as follows: the P(NEt₂)₂ group was first converted to P(Cl)NEt₂ by HCl, and then R (R = ^tBu, ⁿBu, and Ph) was introduced to give P(R)NEt₂, which was again allowed to react with HCl to form the P(Cl)R group. Of the three diphospha[2] ferrocenophanes, (P^tBu)₂-bridged [2]ferrocenophane (10a) could be isolated as free diphosphine, while because of difficulty in their isolations as free ligands, the ⁿBu and Ph analogs (10b and 10c, respectively) were characterized as bis(pentacarbonylmetal) complexes (μ-10b)-[W(CO)₅]₂ (11) and (μ-10c)-[Cr(CO) ₅]₂ (12), in which the respective phosphorus centers were coordinated to the pentacarbonylmetal fragments. X-ray analysis was performed for the three diphospha[2]ferrocenophanes, 10a, 11, and 12, demonstrating that their P - P bond lengths are 2.3093(7), 2.261(5), and 2.2502(8) A?, respectively. Because these tether P - P lengths are smaller than an ideal distance between the two parallel C₅H₅ rings of ferrocene, the two C₅H₄ rings of each of 10a, 11, and 12 are inclined from the parallel by 12.9°, 9.7°, and 13.6°, respectively. DFT calculations were performed on (PH)₂-bridged [2]ferrocenophane as a model-compound, and showed that there are two conformational isomers. One, named the parallel form, features a P - P bond that is almost parallel to the axis passing through the centers of the two C₅H₄ rings, while the P - P bond of the other, named the twist form, leans with the two C₅H₄ rings twisted. The smaller inclined angle of 9.7° observed for 11 was found to result from its parallel-form conformation, while the C₅H₄ rings of 10a and 12 were more inclined due to adoption of the twist-form conformation.

Full text of DOI:10.1016/j.jorganchem.2012.04.022

Journal of Organometallic Chemistry 713 (2012) 80e88
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of [2]ferrocenophanes containing trivalent diphosphine units
*
Yoshikazu Tanimoto, Yuko Ishizu, Kazuyuki Kubo, Katsuhiko Miyoshi, Tsutomu Mizuta
Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan
a r t i c l e i n f o
a b s t r a c t
Three (PR)2-bridged [2]ferrocenophanes (R ¼ tBu (10a), nBu (10b), and Ph (10c)) in which the two C5H4
rings of the ferrocene unit were bridged with a P(III)dP(III) bond were synthesized via Mg-mediated
reductive coupling between the phosphorus centers of corresponding [Fe{C5H4P(Cl)R}2]. The P(Cl)R
groups of [Fe{C5H4P(Cl)R}2] were derived from the P(NEt2)2 groups of [Fe{C5H4P(NEt2)2}2] as follows: the
P(NEt2)2 group was first converted to P(Cl)NEt2 by HCl, and then R (R ¼ tBu, nBu, and Ph) was introduced
to give P(R)NEt2, which was again allowed to react with HCl to form the P(Cl)R group. Of the three
diphospha[2]ferrocenophanes, (PtBu)2-bridged [2]ferrocenophane (10a) could be isolated as free
diphosphine, while because of difficulty in their isolations as free ligands, the nBu and Ph analogs (10b
Article history:
Received 7 January 2012
Received in revised form
11 April 2012
Accepted 19 April 2012
Keywords:
(PR)2-bridged [2]ferrocenophane
Diphosphine ligand
Reductive coupling
Binuclear complex
and 10c, respectively) were characterized as bis(pentacarbonylmetal) complexes (m-10b)-[W(CO)5]2 (11)
and ( -10c)-[Cr(CO)5]2 (12), in which the respective phosphorus centers were coordinated to the pen-
m
tacarbonylmetal fragments. X-ray analysis was performed for the three diphospha[2]ferrocenophanes,
10a, 11, and 12, demonstrating that their PdP bond lengths are 2.3093(7), 2.261(5), and 2.2502(8) Å,
respectively. Because these tether PdP lengths are smaller than an ideal distance between the two
parallel C5H5 rings of ferrocene, the two C5H4 rings of each of 10a, 11, and 12 are inclined from the parallel
by 12.9ꢀ, 9.7ꢀ, and 13.6ꢀ, respectively. DFT calculations were performed on (PH)2-bridged [2]ferroceno-
phane as a model-compound, and showed that there are two conformational isomers. One, named the
parallel form, features a PdP bond that is almost parallel to the axis passing through the centers of the
two C5H4 rings, while the PdP bond of the other, named the twist form, leans with the two C5H4 rings
twisted. The smaller inclined angle of 9.7ꢀ observed for 11 was found to result from its parallel-form
conformation, while the C5H4 rings of 10a and 12 were more inclined due to adoption of the twist-
form conformation.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
(NPCl2)3 [6b,c]. Recently, Pietschnig reported the formation of
diphospha[2]ferrocenophane (1b) starting from a unique 1,10-
Phosphorus-bridged [n]ferrocenophanes (n ¼ 1 and 2, denoting
the number of bridging elements covalently tethering two cyclo-
pentadienyl rings of ferrocene) are attractive phosphorus ligands,
since their ferrocene units are strained due to the short tether
connecting the two C5H4 rings [1]. Although phosphorus-bridged
[1]ferrocenophanes have been extensively studied during the past
two decades as useful precursors for the preparation of valuable
materials by ring-opening reactions [2e5], studies on diphospha[2]
ferrocenophanes are limited. Only two diphospha[2]ferroceno-
phanes have been prepared so far [6]. Allcock isolated a trace
amount of bis(triphosphazene)-bridged [2]ferrocenophane (1a in
Chart 1) from a reaction mixture obtained by a treatment of dili-
thioferrocene with an excess amount of hexachlorotriphosphazene,
bis(phosphenyl)-ferrocene, Fe(C5H4eP¼PeR)2 [6a]. In both
diphospha[2]ferrocenophanes, however, one or both of the two
bridging phosphorus centers are pentavalent. There is thus far no
example of a [2]ferrocenophane tethered with two trivalent
phosphorus centers that are available for coordination to metal
fragments.
On the other hand, many types of [2]ferrocenophanes tethered
with main group heteroatoms other than phosphorus have been
prepared and their structures have been determined by X-ray
analysis [7e10]. Selected examples in which both bridging atoms
are the same element are listed in Chart 1 and Table 1, where
geometric parameters are given to characterize the distortions. The
definitions of
a, b, d, q, and s are illustrated in Chart 2 [11]. The
smallest
a
angle of 0.7ꢀ is observed for distanna[2]ferrocenophane
(2), which has the longest tether SneSn bond of 2.7622(5) Å [7f].
Digerma- and disila[2]ferrocenophanes 3 and 4 respectively, have
* Corresponding author. Tel.: þ81 82 424 7420; fax: þ81 82 424 0729.
E-mail address: mizuta@sci.hiroshima-u.ac.jp (T. Mizuta).
shorter EeE bonds (E ¼ heteroatom) and larger
a angles than the
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.04.022

Y. Tanimoto et al. / Journal of Organometallic Chemistry 713 (2012) 80e88
81
Fig. 2. Molecular structure of 11. Ellipsoids are shown at 50%. Hydrogen atoms are
omitted for clarity. The selected bond distances (Å) and angles (ꢀ): W1eP1 2.530(3),
W2eP2 2.519(3), FeeC1 2.008(13), FeeC6 2.009(12), P1eC1 1.828(13), P1eC11 1.831(12),
P1eP2 2.262(4), P2eC6 1.826(13), P2eC15 1.852(11), C1eP1eP2 101.4(4),
C11eP1eP2
101.4(4), C1eP1eW1 115.9(4), C11eP1eW1 116.2(5), P2eP1eW1 117.72(14), C6eP2eP1
101.8(4), C15eP2eP1 100.0(4), C6eP2eW2 114.9(4), C15eP2eW2 118.5(4), P1eP2eW2
117.47(15).
Fig. 1. Molecular structure of 10a. Ellipsoids are shown at 50%. Hydrogen atoms are
omitted for clarity. The selected bond distances (Å) and angles (ꢀ): FeeC1 2.008(2),
FeeC6 2.013(2), P1eC1 1.840(2), P1eC11 1.887(2), P1eP2 2.2502(8), P2eC6 1.835(2),
To prepare diphospha[2]ferrocenophane by the “flytrap”
method, a free C5H5ePRPReC5H5 ligand is required, but trivalent
phosphines having a C5H5 group are known to be unstable [15]. To
date, the only example of the free ligand is an indenyl derivative
PtBu(Ind)PtBu(Ind) (Ind ¼ 1H-inden-2yl) [16]. Dihalodiphosphines
PRXePRX (X ¼ Cl, Br, and I) for the second route are also difficult to
handle because they are very sensitive to moisture and air [17].
P2eC15 1.893(2), C1eP1eC11 102.37(10), C1eP1eP2 96.49(8),
C11eP1eP2 106.02(9),
C6eP2eC15 102.87(10), C6eP2eP1 96.91(8), C15eP2eP1 106.36(9).
distanna[2]ferrocenophane 2 [8c,9b,9i]. The angle further increases
for diphospha analogs 1a and 1b, and in the dibora analogs 5a and
5b, the strain is the largest, judging from their
a and b angles
[10b,10f]. If the P(III)eP(III) length of (PR)2-bridged [2]ferroceno-
phane is assumed to be comparable to those of trivalent diphos-
phines R2PePR2, for example, 2.212(1) Å of Me2PePMe2 [12],
2.217(1) Å of Ph2PePPh2 [13], and 2.2345(9) Å of tBu2PePtBu2 [14],
(PR)2-bridged [2]ferrocenophane is anticipated to have a strain
comparable to those of 1a and 1b, meaning that they would have
a sufficient thermodynamic stability for isolation.
In this paper, we report our synthetic work on (PR)2-bridged [2]
ferrocenophanes, and discuss the distortion associated with
different crystal structures.
2. Results and discussion
2.1. Preparation of diphospha[2]ferrocenophane
Various synthetic routes have been developed to prepare [2]
ferrocenophanes [11]. Most of them can be classified into the three
types shown in Scheme 1: (i) the “flytrap” method in which the two
C5H5 rings tethered in advance are allowed to react with FeCl2 in
the presence of an appropriate base [9c,10b,10f], (ii) the salt
metathesis between 1,10-dilithioferrocene and E(R)nXeE(R)nX
(E ¼ B, Si, and Ge, X ¼ Cl) [7a,8c,8f,9i,10f], and (iii) the ring
closure of 1,10-disubstituted ferrocene Fe{C5H4E(R)nX}2 (E ¼ Si, Ge,
Sn, and P, X ¼ H, Cl, OEt, and SiR3) by reduction with metal
[6,7f,8a,9b].
Fig. 3. Molecular structure of 12. Ellipsoids are shown at 50%. Hydrogen atoms are
omitted for clarity. The selected bond distances (Å) and angles (ꢀ): FeeC1 1.995(2),
FeeC6 2.000(2), Cr1eP1 2.4144(6), Cr2eP2 2.4294(6), P1eC1 1.818(2), P1eC11 1.836(2),
P1eP2 2.3100(7), P2eC6 1.823(2), P2eC17 1.836(2), C1eP1eP2 97.19(7),
C11eP1eP2
105.30(7), C1eP1eCr1 116.77(7), C11eP1eCr1 112.06(7), P2eP1eCr1 121.90(3), C6eP2eP1
97.23(7), C17eP2eP1 103.28(7), C6eP2eCr2 116.33(7), C17eP2eCr2 110.86(6), P1eP2eCr2
123.88(3), O2eC24eCr1 170.6(2), O6eC28eCr2 170.5(2).

82
Y. Tanimoto et al. / Journal of Organometallic Chemistry 713 (2012) 80e88
Chart 2. Definitions of a, b, d, q, and s (see ref. [11] for details).
Fig. 4. Optimized geometries of 13 in parallel form (left) and twist form (right).
Hydrogen atoms are omitted for clarity. Lone pairs on the phosphorus centers are
tentatively indicated with broken lines.
Therefore, the stepwise introduction of R and Cl to the phosphorus
centers was employed using the NEt2 group as a temporal
substituent that could be readily replaced with Cl by a treatment
with PCl3 or HCl.
31
The P{1H} NMR spectrum of 1,10-bis(chloro(diethylamino)
Therefore, we selected the third method in Scheme 1 for the
preparation.
phosphino)ferrocene (7) consists of two signals at 134.6 and
134.9 ppm with a ratio of 1:1 due to two diastereomers arising from
the two asymmetric phosphorus centers. After substitution of Cl on
the phosphorus centers with R groups, the signals shifted to 73.8
and 73.9 ppm for R ¼ tBu (8a), 44.1 and 44.7 ppm for R ¼ nBu (8b),
and 54.3 and 54.4 ppm for R ¼ Ph (8c). The diethylamino groups of
8a were replaced with Cl by a reaction with HCl/Et2O to afford 9a.
The 31P{1H} NMR spectrum of 9a in the reaction mixture showed
signals at 111.2 and 112.5 ppm, which were very close to the value of
109.1 ppm for PhtBuPCl and 111.2 ppm for FctBuPCl (Fc ¼ ferrocenyl)
[21,22]. Since the spectrum indicated almost complete trans-
formation from 8a to 9a, 9a was used for reduction without puri-
fication. After stirring with Mg overnight, the reaction mixture
exhibited a new 31P{1H} NMR signal at 20.6 ppm, suggesting that
only one diastereomer was formed. Further reaction with Mg,
however, resulted in the appearance of several signals around
ꢁ26 ppmdthat is, in the range of signals of R2Pꢁ anions such as
(Ph2P)2Mg (ꢁ41 ppm) [23], suggesting cleavage of the PdP bond.
The species having the 31P{1H} NMR signal at 20.6 ppm could be
isolated with a deactivated Al2O3 column, and determined to be
(PtBu)2-bridged [2]ferrocenophane 10a by using 1H and 13C{1H}
NMR as well as X-ray analysis. The yield of 10a was moderate (63%).
To achieve the ring closure reaction, the procedures for the less
strained distanna- and digerma[2]ferrocenophanes 2 and 3b in
Table 1 are very informative [7f,8a]. These compounds were
synthesized by the reductive coupling reactions of 1,10-disubsti-
tuted ferrocene Fe{C5H4ER2X}2 (X ¼ Cl and OMe) with metals.
Likewise, the PeP bond of diphosphine R2PePR2 can be formed by
a reaction of R2PCl with Li or Na [18]. We therefore expected that
the ring closure reaction would be possible by reducing Fe
{C5H4P(Cl)R}2 with metals. However, since diphospha[2]ferroce-
nophane is more strained than 2 and 3b, a strongly reducing metal
might lead to a further reduction that cleaves a once formed PeP
bond to give a 1,10-bis(phosphide)ferrocene dianion. Therefore,
Mg was selected as a milder reducing reagent than Li and Na.
Bis(alkylchlorophosphino)ferrocene was prepared in accor-
dance with Scheme 2, where 1,10-dilithioferrocene is first converted
to bis(diaminophosphino)ferrocene (6)[19,20], the phosphorus
groups of which are successively transformed to P(Cl)NEt2 (7), P(R)
NEt2 (8), and P(Cl)R (9) (R ¼ tBu, nBu, and Ph). The multistep
reactions using the NEt2 group are essential for the synthesis,
because
a direct reaction of dilithioferrocene with alkyldi-
chlorophosphine PRCl2 gives not 9 but PR-bridged [1]ferroceno-
phane as a main product even if PRCl2 is used in excess [1,2].
Table 1
Geometric parameters of selected [2]ferrocenophanes tethered with an EeE bond
(E ¼ main group heteroatom).
Compound
E
EeE distance aa
ba,b
qa,b
da
sa
Ref.
2
Sn 2.7622 (5)
Ge 2.418 (1)
Ge 2.431 (1)
Si 2.3535 (9)
0.7 10.5
3.9 10.1
4.9 9.6
4.2 10.8
2.6 8.9
6.0 12.2
6.6 10.2
6.6 11.8
12.9 12.4
9.7 9.5
97.6
179.4 2.9 7f
176.5 5.0 8c
175.1 10.5 8a
176.5 6.6 9h
175.9 2.9 9b
175.9 24.3 9b
175.4 19.5 9b
175.8 23.5 9b
3a
3b
4a
4bc
101.6
100.8
102.8
101.7
99.9
100.2
100.3
97.2
Si
Si
Si
Si
P
2.390 (3)
2.396 (3)
2.362 (3)
2.373 (3)
2.3100 (7)
2.262 (4)
2.2502 (8)
2.22 (1)
12
11
10a
1b
173.2 36.5 This work
173.5 16.5 This work
170.9 32.8 This work
P
P
P
101.6
96.7
13.6 10.8
11.5 14.0d,e 95.6d,e 172.5 34.7 6a
15.0d,f 100.9d,f
1a
5a
5b
P
B
B
2.2187 (5)
1.724 (3)
1.698 (4)
7.7 13.2
12.8 21.2
10.5 25.3
103.1
109.8
107.2
176.2 20.2 6c
170.1 27.6 10f
173.4 38.3 10b
a
Definitions are illustrated in Chart 2.
b
c
d
e
f
An average value.
Four crystallographically independent molecules are present in a unit cell.
The values are not averaged because of difference in substituents.
The value at the trivalent phosphorus center.
Chart 1. Selected [2]ferrocenophanes tethered with main group heteroatoms.
The value at the pentavalent phosphorus center.

Y. Tanimoto et al. / Journal of Organometallic Chemistry 713 (2012) 80e88
83
species. A 31P{1H} NMR spectrum of the reaction mixture consisted
of a singlet at 8.7 ppm, a multiplet at ꢁ37 ppm, and two doublets
at ꢁ41 ppm and ꢁ72 ppm. Based on the similarity of the chemical
shift to that of 10a, the signal at 8.7 ppm is assigned to the desired
(PnBu)2-bridged [2]ferrocenophane 10b, and the signals
around ꢁ40 ppm might be those of anionic phosphide species
together with Mg2þ cation. Phosphide magnesium has been
reported to form aggregates [23], which could have been respon-
sible for the observed multiplet. The signal at ꢁ70 ppm had a low
intensity and could not be characterized. An intensity ratio of 10b
vs. the total of other signals varied from 1:3 to 1:1, depending on
the conditions of the activated magnesium turnings, which were
prepared by vigorous stirring with a magnetic bar for several hours
under a nitrogen atmosphere [26]. The better yield of 10b was
attained when isolated 9b was used. The reduction required several
t
hours to overnight, but unlike in the case of the Bu analog, pro-
longed reaction time did not increase the amount of byproducts,
although excess magnesium remained. This result suggests that
byproducts were formed not by the reaction of magnesium with
the formed 10b, but by the direct reaction between 9b and
magnesium. Because of the lower yield and difficulty in isolation,
10b was transformed to a metal complex to characterize the
diphospha[2]ferrocenophane framework.
Scheme 1. Three major methods for preparation of [2]ferrocenophanes.
The reaction mixture containing 10b was subjected to further
reaction with [W(CO)5(thf)]. The 31P{1H} NMR signal at 8.7 ppm
assigned to 10b disappeared after the reaction, and a new signal at
75.4 ppm having satellite signals due to 183W(I ¼ 1/2) suggested
formation of the ditungsten complex of 10b. This species was iso-
lated by Al2O3 column chromatography, which decreased its yield
to 6%. In the 13C{1H} NMR spectrum, several carbon atoms of nBu
and C5H4 groups were observed as triplets, which are characteristic
of the diphospha[2]ferrocenophane framework. The molecular
structure determined by X-ray analysis is shown in Fig. 2, where
two W(CO)5 fragments are coordinated to the two phosphorus
centers of 10b to form the ditungsten complex (11). The two C5H4
rings of the ferrocene moiety of 11 are tethered by the PeP bond,
and the two nBu groups adopt a trans disposition with respect to
the PdP bond. It is noteworthy that the free tBu analog 10a did not
react at all with [W(CO)5(thf)], probably due to the much larger
steric bulkiness of the tBu group than the nBu group.
The 1H NMR of 10a consisted of five signals, four of which were
assigned to the two C5H4 rings and one of which was assigned to
the tBu groups. It is noteworthy that the tBu signal was observed as
a virtual triplet due to the strong coupling between the two
phosphorus centers, proving the direct PdP bond. The 13C{1H}
NMR spectrum also showed virtual triplets for tBu and three of five
carbons of each C5H4 ring.
The structure of 10a was finally confirmed by X-ray analysis as
shown in Fig. 1, which indicates that the product obtained is the
t
racemic isomer. The two Bu groups on the phosphorus centers of
10a in Fig. 1 adopt a trans disposition with respect to the PeP bond.
Since these two tBu groups are disposed on mutually opposite sides
with respect to the PeP bond, the racemic isomer is considered to
be more stable than the meso isomer in which the two tBu groups
will be disposed on the same side [24,25]. The deformation
parameters of the [2]ferrocenophane group will be discussed in
a separate section.
The Ph analog 10c was also prepared by magnesium reduction of
the corresponding 1,10-bis(phenylchlorophosphino)ferrocene 9c. A
31P{1H} NMR signal of 10c was observed at 4.6 ppm together with
those of byproducts at ꢁ23 and ꢁ60 ppm. The intensity ratio of
10c:others varied from 1:trace to 1:0.75, probably depending on the
activity of magnesium. Although 10c was formed in a relatively
better yield than that of 10b, it was found that decomposition took
place upon concentrating the solution of 10c, even after removal of
the remaining magnesium by filtration. Thus, the reaction of 10c
with a metal complex was again conducted to characterize 10c as its
metal complex. First, [W(CO)5(thf)] was used, but the 31P{1H} NMR
spectra of the reaction mixture indicated that the intensity of the
signal assigned to the bis(pentacarbonyltungsten) complex was low
[27]. Next, as a more reactive metal fragment, chromium carbonyl
complex [Cr(CO)5(thf)] was allowed to react with 10c. The reaction
proceeded slowly, taking two days for completion. During the
reaction, a pair of doublets were observed at 76.1 and 33.7 ppm with
JPP ¼ 212 Hz, which can be assigned to a species having a single
The nBu and Ph analogs of 10a could be synthesized by a method
similar to that used for 10a. These analogs, however, were found to
be less stable than 10a. In the case of the nBu analog, treatment of
aminophosphine 8b with HCl afforded chlorophosphine 9b, which
was then reduced with Mg to result in the formation of several
Cr(CO)5 moietyonone of the twophosphoruscenters. Finally, the 31
P
{1H} NMR signal of free 10c at 4.6 ppm disappeared completely, and
instead a new signal appeared at 98.6 ppm that was assigned to the
desired dichromium complex 12. The complex 12 could be purified
by recrystallization. The molecular structure was determined by X-
ray analysis, and is given in Fig. 3. Details of the structure are dis-
cussed together with those of 10a and 11 in the next section.
Scheme 2. Preparation of diphospha[2]ferrocenophanes.

84
Y. Tanimoto et al. / Journal of Organometallic Chemistry 713 (2012) 80e88
2.2. Molecular structures of diphospha[2]ferrocenophane
(PH)2-bridged [2]ferrocenophane (13) was calculated. Structural
optimizations were performed for the two conformational
isomers illustrated in Fig. 4, and energy minimums were estab-
lished for both these isomers. The left structure features a PeP
bond that is almost parallel to the axis passing though the
The PeP bond lengths of the free diphospha[2]ferrocenophane
10a, and the two metal complexes 11 and 12 were 2.2502(8),
2.262(4), and 2.3100(7) Å, respectively, and these values were
almost comparable to those of the previously reported 1a and 1b
[6]. These five PeP bonds listed in Table 1 are shorter than the SieSi
bonds of disila[2]ferrocenophanes 4a and 4b around 2.35e2.40 Å,
due to the smaller covalent radius of the phosphorus atom
compared to the silicon atom. Looking at Table 1, in which the
compounds are arranged by their EeE distances, the shorter EeE
bonds tend to make the ferrocene unit more distorted. The find-
centers of the two C5 rings. Its
on the right side of Fig. 4, the two C5H4 rings are twisted, with the
PeP bond leaning. Its
angle increases to 24.20ꢀ. Hereafter, the
s
angle is 1.51ꢀ. In the other isomer
s
former conformation is referred to as the parallel form, while the
latter is called the twist form. To compare the distortions between
the parallel and twist forms, their deformation parameters are
summarized in Table 2. The smaller
form suggest that the parallel form is less distorted than the twist
form. On the other hand, the smaller C(ipso)ePeP
angle of 99.6ꢀ
for the twist form is closer to the CePeP angle of 98.30(5)ꢀ for
Me2PePMe2, which can be regarded as the angle without steric
strain [12], and also close to those of the more common trivalent
phosphines [31]. As far as the angle is concerned, the twist form
a and b angles of the parallel
ings that the
a angles of diphospha[2]ferrocenophanes in the range
of 7.7e13.6ꢀ are larger than those of disila[2]ferrocenophanes 3a
and 3b is consistent with this trend. On closer inspection, however,
the five PeP lengths given in Table 1 are found not to correlate with
q
q
their
largest
because it has the smallest PeP length (2.2187(5) Å), but in fact the
opposite is true: 1a exhibits the smallest
angle of 7.7ꢀ. This
a
angles. For example, it is expected that 1a will have the
a
angle among the five diphospha[2]ferrocenophanes,
q
is considered to be less distorted. In this way, since the latter
factor exhibits an opposite trend compared to the former factor,
the total energies of the two isomers become almost comparable.
The total energies calculated for the two isomers indicate that the
twist form is more stable by only 0.19 kcal/mol compared to the
parallel form.
a
puzzling relationship can be rationalized if the twisting of the two
C5H4 rings is taken into consideration. The more the two C5H4 rings
are twisted, the larger the
s angle is, with the PeP bond leaning
with respect to the vector passing through the respective centers of
the two C5 rings. This twisting inclines the C5H4 rings, leading to an
The small difference in the total energy between the two
conformational isomers clearly indicates that the substituents on
the phosphorus centers certainly affect the conformation preferred
for an actual molecule. The free ligand 10a has the bulky tBu group
on each phosphorus center, bearing the twist form as shown in
Fig. 1. Looking at the parallel form of (PH)2-bridged [2]ferroceno-
phane 13 shown in Fig. 4a, the hydrogen atom on the phosphorus
center is almost coplanar with the C5H4 group, and therefore if the
H atom of the parallel form is replaced with the tBu group, a severe
increment of the
that the P1eP2 bond of 10a leans by 32.8ꢀ, which contributes to its
large angle, while the P1eP2 bond of 11 leans least among the five
diphospha[2]ferrocenophanes, resulting in a smaller angle rela-
a angle. The molecular structure in Fig. 1 indicates
a
a
tive to 12, which has a comparable P1eP2 bond but a much larger
angle compared with 11.
s
To clarify the relationship between the
a and s angles, DFT
calculation was conducted. The free ligand 10a was first calculated
using the B3LYP and mPWPW91 methods [28,29]. Although B3LYP
is commonly used for the DFT calculation of metal complexes,
mPWPW91 more precisely reproduced the experimental bond
lengths of 10a [30], as listed in Table 2. The average distance
between Fe and the centers of the C5 rings was 1.635 Å for the
optimized structure calculated by the mPWPW91 method, which
is very close to the experimental value of 1.641 Å, while the cor-
responding value was 1.671 Å when using the B3LYP method. The
experimental PeP bond length of 2.250 Å was also closer to the
2.267 Å obtained by the mPWPW91 method than the 2.298 Å by
the B3LYP method. A similar trend held for the PeC bonds.
Therefore, mPWPW91 was employed in the following DFT
calculations.
t
steric congestion is anticipated between the Bu and C5H4 groups.
To estimate the difference in the total energy between the parallel
and twist forms of 10a, we tried to optimize the structure of 10a in
the parallel form, but could not find a stationary point with the
parallel form. Instead, the optimization starting from the parallel
form resulted in the twist form.
In contrast, a parallel form was adopted by 11 that has nBu and
W(CO)5 groups on each phosphorus center. In this case, the steric
demand from the nBu group was reduced significantly compared to
the tBu group of 10a, and the W(CO)5 groups, which are more bulky
than the nBu groups, occupy open space above and below the
ferrocene unit. In the case of 12, since the steric bulkiness of Cr(CO)5
is almost comparable to that of W(CO)5, one might expect that 12
would also adopt the parallel form in the manner of 11, but as
shown in Fig. 3, it adopts the twist form instead. In this case, the
two bulky Cr(CO)5 groups cause the phenyl groups to orient their
edges to the ferrocene unit. If 12 adopts a parallel form, the ipso
carboneP bonds C11eP1 and C17eP2 must be almost coplanar with
the C5H4 rings as in Fig. 2, and therefore the ortho CeH groups of
the Ph rings exert severe steric congestion against the C5H4 ring.
Instead, as in Fig. 3, the CreP bonds are located at the position
coplanar to the C5H4 ring, and the CO groups on Cr can avoid
congestion by locating the edge of the C5H4 group between two CO
groups. The dihedral angles are 33.2(1)ꢀ for C1eP1eCr1eC23, and
33.9(1)ꢀ for C6eP2eCr2eC31. It is noteworthy that the O2 atom of
the carbonyl group on the Cr1 is in van der Waals contact with C19
and C20 of the Ph group on the adjacent P2 atom. The distances are
3.196(3) Å for O2$$$C19 and 3.213(3) Å for O2$$$C20. As a result, the
Cr1eC24eO2 angle of 170.6(2)ꢀ deforms by 9.4ꢀ from a linear
arraignment, and the C24eCr1eP1 angle increases to 102.28(7)ꢀ. A
similar situation is also found between the other Cr(CO)5 and Ph
groups.
Next, in order to examine the structural features of diphospha
t
[2]ferrocenophane without a steric demand from the Bu groups,
Table 2
Structural parameters obtained by DFT calculations on diphospha[2]
ferrocenophanes.
compound
Substituent
10A
tBu
10A
tBu
10A
tBu
Parallel-13
Twist-13
H
H
Method
Exp
mPWPW91
12.55
11.60
96.71
172.48
33.66
1.635
2.267
1.840
B3LYP
13.81
10.64
97.07
171.91
32.33
1.671
2.298
1.852
mPWPW91
10.36
7.49
102.48
173.58
1.51
1.640
2.245
1.841
mPWPW91
11.14
9.88
99.61
173.33
24.18
1.640
2.265
1.836
ꢀ
a
b
/
/
13.58
10.82c
96.70c
170.86
32.80
1.641c
2.250
1.838c
ꢀ
ꢀ
ꢀ
ꢀ
q
d
/
/
s/
FeeCpcent/Åa
PeP/Å
PeCpipso/Åb
a
A distance between Fe and the center of the C5 ring.
A distance between P and the ipso carbon of the C5H4 ring.
An average value.
b
c

Y. Tanimoto et al. / Journal of Organometallic Chemistry 713 (2012) 80e88
85
3. Conclusions
product was found to be a mixture of racemic and meso isomers in
a ratio of 1:1. The following NMR chemical shifts with an asterisk
indicate two different signals due to racemic and meso isomers.
Three (PR)2-bridged [2]ferrocenophanes (R ¼ tBu (10a), nBu
(10b), and Ph (10c)) in which the two C5H4 rings of the ferrocene
unit were bridged with a P(III)eP(III) bond were synthesized via
Mg-mediated reductive coupling between phosphorus centers of
corresponding [Fe{C5H4P(Cl)R}2]. These are the first diphospha[2]
ferrocenophanes in which both of the bridging atoms are P(III),
although P(V)-bridged analogs have been reported previously. Of
the three diphospha[2]ferrocenophanes prepared, the P(III) centers
of 10b and 10c were demonstrated to be available for coordination
to a metal fragment such as M(CO)5 (M ¼ W and Cr, respectively),
while 10a did not react with metal fragments probably due to steric
congestion from the bulky tBu group. The X-ray crystal structures as
well as the DFT calculations indicated that these diphospha[2]fer-
rocenophanes are strained molecules due to their PeP lengths
being smaller than the ideal distance between two parallel C5H5
rings of ferrocene. The deformation of these ferrocene units
showed an interesting dependence on their conformations. It was
found that the two conformations, that is, parallel and twist forms
are possible for (PR)2-bridged [2]ferrocenophane, and that the
twist form made the C5H4 rings of the ferrocene unit more inclined.
1H NMR (300.4 MHz, C6D6):
d
¼ 1.11 (t, JHH ¼ 7.1 Hz, 12H, Et),
1.19* and 1.23* (d, JPH ¼ 1.1, 18H, Bu), 3.02e3.16 (m, 8H, Et),
4.39e4.14 (br, 8H, C5H4); 13C{1H} NMR (74.5 MHz, C6D6):
d
¼ 15.3 (s,
Et), 28.2 (d, JPC ¼ 17 Hz, Bu), 34.1 (d, JPC ¼ 18 Hz, Bu), 46.3* and 46.5*
(d, JPC ¼ 17 and 16 Hz, Et), 71.6 (br, JPC ¼ 3 Hz, C5H4), 71.8 (br, C5H4),
72.4* and 72.5* (d, JPC ¼ 5 and 4 Hz, C5H4), 73.1* and 73.2* (d,
JPC ¼ 22 and 23 Hz, C5H4), 80.4* and 80.5* (d, JPC ¼ 23 Hz, ipso-
C5H4); 31P{1H} NMR (121.5 MHz, C6D6):
d
¼ 73.8* and 73.9* (s).
4.3. [Fe{h
5-C5H4P(nBu)(NEt2)}2] (8b)
[Fe{C5H4P(NEt2)2}2] (2.75 g, 5.15 mmol) was converted to [Fe
{C5H4PCl(NEt2)}2] (1.27 g) in a manner similar to that described
above. To [Fe{C5H4PCl(NEt2)}2] dissolved in diethyl ether (20 mL)
was added nBuLi (1.6 M hexane solution, 5.1 mL) at room temper-
ature. The reaction mixture was stirred for 2 h. The solvent was
removed under reduced pressure. Flash column chromatography
(deactivated Al2O3, hexane) and workup afforded [Fe
{C5H4P(nBu)(NEt2)}2] (1.26 g, 49%) as a dark orange liquid. The
product was found to be a mixture of racemic and meso isomers in
a ratio of 1:1. In the following, the NMR chemical shifts with an
asterisk indicate two different signals due to racemic and meso
isomers.
4. Experimental section
4.1. General remarks
1H NMR (300.4 MHz, C6D6):
1.13* and 1.15* (t, JHH ¼ 7.1 and 6.5 Hz, 6H, Bu), 1.55e2.15 (m, 12H,
Bu), 2.85e3.10 (m, 8H, Et), 4.24 (m, 2H, C5H4), 4.31* and 4.36* (m,
4H, C5H4), 4.50* and 4.52* (s, 2H, C5H4); 13C{1H} NMR (74.5 MHz,
d
¼ 1.04 (t, JHH ¼ 7.1 Hz, 12H, Et),
All reactions were carried out under a dry nitrogen atmosphere
using Schlenk tube techniques. All solvents were distilled and dried
using sodium (for hexane and toluene), sodium/benzophenone (for
ether and THF), or P2O5 (for CH2Cl2). The purified solvents were
stored under nitrogen. [Fe{C5H4P(NEt2)2}2] was prepared according
to methods in the literature [19]. Al2O3 (standardized, Merck) and
other reagents were used as received.
C6D6):
d
¼ 14.4 (s, Bu), 15.4 (s, Et), 24.8 (d, JPC ¼ 14 Hz, Bu), 27.0* and
27.5* (d, JPC ¼ 9 Hz, Bu), 28.6 (d, JPC ¼ 20 Hz, Bu), 43.8 (d, JPC ¼ 15 Hz,
Et), 69.5 (s, C5H4), 70.9 (d, JPC ¼ 16 Hz, C5H4), 72.0* and 72.1* (d,
JPC ¼ 7 and 4 Hz, C5H4), 74.8* and 75.3* (d, JPC ¼ 28 and 29 Hz, C5H4),
81.0* and 81.3* (d, JPC ¼ 17 Hz, ipso-C5H4); 31P{1H} NMR (121.5 MHz,
NMR spectra were recorded on a JEOL LA-300 spectrometer. 1H
and 13C NMR chemical shifts were reported relative to Me4Si and
were determined by reference to the residual solvent peaks. 31P
NMR chemical shifts were reported relative to H3PO4 (85%) used as
an external reference. Elemental analyses were performed with
a PerkineElmer CHNS 2400II elemental analyzer. Mass Spectra
(ESI) were obtained using Thermo Fisher Scientific LTQ Orbitrap XL.
Mass spectral data were reported in units of mass to charge (m/z).
Photolysis was carried out using Pyrex-glass-filtered emission from
a 400 W mercury arc lamp (Riko-Kagaku Sangyo UVL-400P). The
emission lines used and their relative intensities (in parenthesis)
were: 577.0 (69), 546.1 (82), 435.8 (69), 404.7 (42), 365.0 (100),
334.1 (7), 312.6 (38), and 302.2 (9) nm.
C6D6):
d
¼ 44.1* and 44.7* (s).
5-C5H4P(Ph)(NEt2)}2] (8c)
4.4. [Fe{
h
A
diastereomeric mixture of [Fe{C5H4PCl(NEt2)}2] (0.38 g,
0.82 mmol) was prepared in a manner similar to that described
above. To [Fe{C5H4PCl(NEt2)}2] dissolved in hexane (50 mL) was
added PhLi (0.94 M THF solution, 1.83 mL) at room temperature.
The reaction mixture was stirred for 9 h. The mixture was filtered
over celite under a nitrogen atmosphere, and the solvent was
removed under reduced pressure. Flash column chromatography
(deactivated Al2O3, hexane:acetone ¼ 1:1) and workup afforded [Fe
{C5H4P(Ph)(NEt2)}2] (0.43 g, 97%) as a dark orange liquid. The
product was found to be a mixture of racemic and meso isomers in
a ratio of 2:1 or 1:2. In the following, the NMR chemical shifts with
an asterisk indicate two different signals due to racemic and meso
isomers.
4.2. [Fe{h
5-C5H4P(tBu)(NEt2)}2] (8a)
[Fe{C5H4P(NEt2)2}2] (1.07 g, 2.06 mmol) was placed in a Schlenk
tube. Diethyl ether (20 mL) and PCl3 (0.34 mL, 3.89 mmol) were
added successively and the reaction mixture was refluxed over-
night. The solvent and volatiles were removed under reduced
pressure. The resulting orange solid was washed with hexane, and
dried again in vacuo. [Fe{C5H4PCl(NEt2)}2] (0.74 g) thus obtained
was used without further purification. To [Fe{C5H4PCl(NEt2)}2]
dissolved in diethyl ether (20 mL) was added tBuLi (1.6 M pentane
solution, 2.1 mL) at ꢁ55 ꢀC. The reaction mixture was stirred for
30 min while keeping the temperature at ꢁ55 ꢀC, then allowed to
warm to room temperature, and stirred for 3 h. The mixture was
filtered over celite under a nitrogen atmosphere, and the solvent
was removed under reduced pressure. Flash column chromatog-
raphy (deactivated Al2O3, hexane) and workup afforded [Fe
{C5H4P(tBu)(NEt2)}2] (0.74 g, 71%) as a dark orange liquid. The
1H NMR (300.4 MHz, C6D6):
d
¼ 0.99* and 0.98* (t, JHH ¼ 14.1 Hz,
12H, Et), 2.96e3.14 (m, 8H, Et), 4.17* and 4.23* (m, 2H, C5H4), 4.37*
and 4.39* (m, 2H, C5H4), 4.47* and 4.45* (s, 2H, C5H4), 4.49* and
4.56* (s, 2H, C5H4), 7.13e7.20 (m, 2H, Ph), 7.23e7.31 (m, 4H, Ph),
7.73e7.81 (m, 4H, Ph); 31P{1H} NMR (121.5 MHz, C6D6):
d
¼ 54.3*
and 54.4* (s).
4.5. [Fe{C5H4P(tBu)}2] (10a)
[Fe{C5H4P(tBu)(NEt2)}2] (0.57 g, 1.1 mmol) and ether (30 mL)
were placed in a Schlenk tube. To the solution was added HCl (1.0 M
diethyl ether solution, 4.5 mL) in a dropwise manner at ꢁ78 ꢀC. The
reaction mixture was allowed to warm to room temperature, and

86
Y. Tanimoto et al. / Journal of Organometallic Chemistry 713 (2012) 80e88
stirred for 3 h. The solvent was removed under reduced pressure
and THF (10 mL) was added to the resulting solid. The mixture was
filtered under a nitrogen atmosphere, and the filter material was
rinsed using THF. The volume of the combined solutions was
reduced to 10 mL under reduced pressure. The solution was added
to a Schlenk tube that was charged with an excess amount of
magnesium turnings (2.0 g, 82.3 mg) activated in advance by
vigorous mechanical stirring with a Teflon-coated stirrer bar over
6 h. The reaction mixture was stirred overnight, and filtered. The
solvent was removed under reduced pressure. The resulting orange
solid was extracted by hexane. Flash column chromatography
(deactivated Al2O3, hexane) and workup afforded [Fe{C5H4P(tBu)}2]
(0.25 g, 63%) as an orange powder.
with an excess amount of magnesium turnings (1.0 g, 41.2 mmol)
activated in advance by vigorous mechanical stirring with a Teflon-
coated stirrer bar over 4 h. The reaction mixture was stirred over-
night, and filtered under nitrogen atmosphere. The 31P{1H} NMR
spectrum of the filtrate consisted of three signals at ꢁ41.7, ꢁ37.5,
and 8.5 ppm, the last signal of which was major, and assigned to [Fe
{C5H4P(nBu)}2]. Isolation was tried, but not successful due to the
instability of this species.
4.9. [Fe{C5H4P(nBu)(W(CO)5)}2] (11)
[Fe{C5H4PCl(nBu)}2] prepared from [Fe{C5H4P(nBu)(NEt2)}2]
(0.31 g, 0.59 mmol) was dissolved in THF (5 mL). The solution was
added to a Schlenk tube that was charged with an excess amount of
magnesium turnings (1.0 g, 41.2 mmol) activated in advance by
vigorous mechanical stirring with a Teflon-coated stirrer bar over
4 h. The reaction mixture was stirred for 6 h, and filtered under
a nitrogen atmosphere. To the solution was added a [W(CO)5(thf)]
solution that was prepared by irradiation of a THF (20 mL) solution
of [W(CO)6] (0.30 g, 0.85 mmol) with a UVevis light for 2 h. After
the mixture was stirred for 4 h, the solvent was removed under
reduced pressure. The resulting solid was extracted by ether. Flash
column chromatography (Al2O3, diethyl ether:acetone ¼ 1:1) and
workup afforded [Fe{C5H4P(nBu)(W(CO)5)}2] (0.041 g, 6.9%) as an
orange powder.
1H NMR (300.4 MHz, C6D6):
3.93 (m, 2H, C5H4), 4.33 (m, 2H, C5H4), 4.63 (m, 2H, C5H4), 5.13 (m,
2H, C5H4); 13C{1H} NMR (74.5 MHz, C6D6):
d
¼ 1.15 (t, JHH ¼ 6.6 Hz, 18H, Bu),
d
¼ 29.8 (t, JPC ¼ 10 Hz,
Bu), 31.5 (t, JPC ¼ 2 Hz, Bu), 68.6 (t, JPC ¼ 13 Hz, C5H4), 70.6 (t,
JPC ¼ 3 Hz, C5H4), 75.0 (s, C5H4), 75.8 (s, C5H4), 82.5 (t, JPC ¼ 22 Hz,
C5H4); 31P{1H} NMR (121.5 MHz, C6D6):
C18H26FeP2: C, 60.02; H, 7.28. Found: C, 59.94; H, 6.87.
d
¼ 20.6 (s). Anal. Calcd for
4.6. [Fe{C5H4PCl(nBu)}2] (9b)
[Fe{C5H4P(nBu)(NEt2)}2] (1.17 g, 2.32 mmol) and ether (30 mL)
were placed in a Schlenk tube. To the solution was added HCl (1.0 M
diethyl ether solution, 9.3 mL) in a dropwise manner at ꢁ65 ꢀC. The
reaction mixture was allowed to warm to room temperature, and
stirred for 2 h. The mixture was filtered under a nitrogen atmo-
sphere, and the solvent was removed under reduced pressure. The
resulting residue was dried in vacuo to give [Fe{C5H4PCl(nBu)}2] as
a dark orange oil (0.97 g, 97%). In the following, the NMR chemical
shifts with an asterisk indicate two different signals due to racemic
and meso isomers.
1H NMR (300.4 MHz, CDCl3):
1.80 (m, 6H, Bu),1.98 (m, 2H, Bu), 2.56 (dt, JHH ¼ 4.0 and 12.0 Hz, 2H,
Bu), 3.67 (m, 2H, Bu), 4.12 (s, 2H, C5H4), 4.48 (s, 2H, C5H4), 5.23 (s,
2H, C5H4), 5.56 (s, 2H, C5H4); 13C{1H} NMR (74.5 MHz, CDCl3):
d
¼ 1.14 (t, JHH ¼ 7.1 Hz, 6H, Bu),
d
¼ 13.5 (s, Bu), 24.2 (t, JPC ¼ 8 Hz, Bu), 28.7 (t, JPC ¼ 4 Hz, Bu), 32.7 (t,
JPC ¼ 15 Hz, Bu), 70.1 (s, C5H4), 73.6 (t, JPC ¼ 4 Hz, C5H4), 75.0 (t,
JPC ¼ 9 Hz, C5H4), 75.5 (s, C5H4), 79.9 (t, JPC ¼ 10 Hz, C5H4), 196.4 (t,
JPC ¼ 3 Hz, CO), 198.5 (d, JPC ¼ 12 Hz, CO); 31P{1H} NMR (121.5 MHz,
1H NMR (300.4 MHz, CDCl3):
1.49 (m, 4H, Bu), 1.60 (br, 4H, Bu), 2.11 (br, 4H, Bu), 4.47 (br, 4H,
C5H4), 4.51 (br, 4H, C5H4); 13C{1H} NMR (74.5 MHz, CDCl3):
d
¼ 0.95 (t, JHH ¼ 7.1 Hz, 6H, Bu),
CDCl3):
d
¼ 75.4 (s, JWP ¼ 150 Hz and JWP ¼ 82 Hz). HRMS (ESI
1
2
positive mode): m/z calcd. for C28H26O10FeP2W2: 1007.9364; found
1007.9355 [M þ].
d
¼ 13.5*
and 13.8* (s, Bu), 23.8 (d, JPC ¼ 9 Hz, Bu), 27.0 (d, JPC ¼ 13 Hz, Bu),
35.5 (d, JPC ¼ 24 Hz, Bu), 72.3 (br, C5H4), 72.8 (br, C5H4), 79.6 (d,
4.10. Attempted synthesis of [Fe{C5H4P(Ph)}2] (10c)
JPC ¼ 35 Hz, C5H4); 31P{1H} NMR (121.5 MHz, C6D6):
d
¼ 95.2 (s).
Anal. Calcd for ether solvate C18H26Cl2FeP2$(C4H10O)0.5: C, 51.31; H,
[Fe{C5H4PCl(Ph)}2] (0.18 g, 0.38 mmol) was dissolved in THF
(10 mL). The solution was added to a Schlenk tube that was
charged with an excess amount of magnesium turnings (1.0 g,
41.2 mmol) activated in advance by vigorous mechanical stirring
with a Teflon-coated stirrer bar over 4 h. The reaction mixture was
stirred for 1 h, and filtered over celite under a nitrogen atmosphere.
6.67. Found: C, 51.34; H, 6.37.
4.7. [Fe{C5H4PCl(Ph)}2] (9c)
[Fe{C5H4P(NEt2)(Ph)}2] (3.69 g, 6.80 mmol) and ether (30 mL)
were placed in a Schlenk tube. To the solution was added PCl3
(1.2 mL, 13.6 mmol). The reaction mixture was refluxed overnight.
The solvent was removed under reduced pressure. The resulting
orange powder was washed with hexane and dried in vacuo to give
[Fe{C5H4PCl(Ph)}2] as an orange powder (2.50 g, 78%). In the
following, the NMR chemical shifts with an asterisk indicate two
different signals due to racemic and meso isomers.
A
31P{1H} NMR spectrum of the filtrate indicated a main singlet at
4.6 ppm accompanied by broad minor signals at ꢁ22.0, 43.0,
81.0 ppm. The major signal was assigned to [Fe(C5H4PPh)2]. Isola-
tion was tried, but was not successful due to the contamination
with impurities.
4.11. [Fe{C5H4P(Ph)(Cr(CO)5)}2] (12)
1H NMR (300.4 MHz, CDCl3):
d
¼ 3.98 (br, 1H, C5H4), 4.18 (br, 1H,
C5H4), 4.37 (br, 2H, C5H4), 4.48 (br, 3H, C5H4), 4.62 (br, 1H, C5H4),
[Fe{C5H4PCl(Ph)}2] (0.098 g, 0.21 mmol) was dissolved in THF
(7 mL). The solution was added to a Schlenk tube that was charged
with an excess amount of magnesium turnings (1.0 g, 41.2 mmol)
activated in advance by vigorous mechanical stirring with a Teflon-
coated stirrer bar over 4 h. The reaction mixture was stirred for 4 h,
and filtered under a nitrogen atmosphere. To the solution was
added a [Cr(CO)5(thf)] solution that was prepared by irradiation of
a THF (15 mL) solution of [Cr(CO)6] (0.12 g, 0.52 mmol) with UVeVis
light for 2 h followed by reduction of the volume to 2 mL under
reduced pressure. After the mixture was stirred for 2 days, the
solvent was removed under reduced pressure. The resulting solid
was extracted by diethyl ether. The solvent was removed under
7.44 (br, 6H, Ph), 7.69e7.74 (br, 4H, Ph); 13C{1H} NMR (74.5 MHz,
CDCl3):
d
¼ 73.0e73.6 (br, C5H4), 79.4 (d, JPC ¼ 32 Hz, C5H4),128.4 (d,
JPC ¼ 8 Hz, Ph), 130.7 (s, Ph), 131.8 (d, JPC ¼ 26 Hz, Ph), 138.5 (d,
JPC ¼ 30 Hz, Ph); 31P{1H} NMR (121.5 MHz, CDCl3):
d
¼ 77.6* (s),
78.3* (s). Anal. Calcd for C22H28Cl2FeP2: C, 56.09; H, 3.85. Found: C,
55.75; H, 3.77.
4.8. Attempted synthesis of [Fe{C5H4P(nBu)}2] (10b)
[Fe{C5H4PCl(nBu)}2] (0.10 g, 0.23 mmol) was dissolved in THF
(5 mL). The solution was added to a Schlenk tube that was charged

Y. Tanimoto et al. / Journal of Organometallic Chemistry 713 (2012) 80e88
87
Table 3
Crystallographic and structural refinement data for 10a, 11, and 12.
References
[1] (a) I. Matas, G.R. Whittell, B.M. Partridge, J.P. Holland, M.F. Haddow, J.C. Green,
I. Manners, J. Am. Chem. Soc. 132 (2010) 13279e13289;
(b) A. Bartole-Scott, A.J. Lough, I. Manners, Polyhedron 25 (2006) 429e436;
(c) P.W. Cyr, A.J. Lough, L. Manners, Acta Crystallogr. Sect. E: Struct. Rep.
Online E61 (2005) m457em459;
10A
11
12
Formula
a/Å
b/Å
C18H26FeP2
16.3630(4)
6.0850(1)
17.8130(6)
90.00
96.693(1)
90.00
1761.53(8)
4
C32H34FeO11P2W2
16.0870(6)
11.2190(3)
20.6970(8)
90.0
99.354(2)
90.0
3685.7(2)
4
C32H18Cr2FeO10P2
15.1650(3)
12.7820(3)
16.6790(2)
90.0
101.425(2)
90.0
3168.98(10)
4
(d) B. Wrackmeyer, O.L. Tok, A. Ayazi, F. Hertel, M. Herberhold, Z. Naturforsch.,
B: Chem. Sci. 57 (2002) 305e308;
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(1985) 109e116;
c/Å
ꢀ
ꢀ
a
/
b
/
ꢀ
/
g
V/Å3
Z
Formula weight
Space group
Temp/ꢀC
360.18
1080.08
P21/c (No. 14)
ꢁ73
784.25
P21/c (No. 14)
ꢁ73
P21/n (No. 14)
ꢁ73
l
/Å
Dcalcd/g cmꢁ3
(Mo K
)/mmꢁ1
(I))
0.71069
1.358
0.71069
1.946
0.71069
1.644
m
a
1.029
0.0391
0.1022
6.757
0.0695
0.1631
1.284
0.0287
0.0749
(l) S. Ikuta, I. Motoyama, H. Sano, Bull. Chem. Soc. Jpn. 57 (1984) 299e300;
(m) M. Clemance, R.M.G. Roberts, J. Silver, J. Organomet. Chem. 243 (1983)
461e467;
R1 (I > 2
s
a
wR2
(n) I.R. Butler, W.R. Cullen, F.W.B. Einstein, S.J. Rettig, A.J. Willis, Organome-
tallics 2 (1983) 128e135;
(o) D. Seyferth, H.P.J. Withers, Organometallics 1 (1982) 1275e1282;
(p) H.P.J. Withers, D. Seyferth, J.D. Fellmann, P.E. Garrou, S. Martin, Organo-
metallics 1 (1982) 1283e1288;
a
wR2 ¼ {S[w(F2o ꢁ Fc2)2]/S[w(Fo2)2]}1/2; w ¼ 1/[
s
2(F2o) þ (ap)2 þ bp]; p ¼ (Fo2 þ 2F2c)/
3. a and b values for 10a, 11, and 12 are 0.0535 and 2.5980, 0.0849 and 64.9794, and
0.0461 and 2.3263, respectively.
(q) A.G. Osborne, R.H. Whiteley, R.E. Meads, J. Organomet. Chem. 193 (1980)
345e357;
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(1980) 91e101;
reduced pressure. The resulting solid was washed four times with
pentane (5 mL aliquots). The orange product was dried in vacuo to
give [Fe{C5H4P(Ph)(Cr(CO)5)}2] (0.126 g, 83%).
(s) D. Seyferth, H.P.J. Withers, J. Organomet. Chem. 185 (1980) C1eC5.
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1H NMR (300.4 MHz, C6D6):
d
¼ 3.90 (br, 2H, C5H4), 4.52 (br, 2H,
C5H4), 5.28 (br, 2H, C5H4), 5.37 (br, 2H, C5H4), 7.04 (t, JHH ¼ 7.4 Hz,
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5205e5211;
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9146e9150;
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Chem. 43 (2002) 500e501;
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447e453;
2H, Ph), 7.16 (br, 4H, Ph), 7.62 (m, 4H, Ph); 13C{1H} NMR (74.5 MHz,
C6D6):
d
¼ 68.1 (t, JPC ¼ 14 Hz, C5H4), 73.4 (t, JPC ¼ 5 Hz, C5H4), 77.6
(s, C5H4), 82.9 (t, JPC ¼ 11 Hz, C5H4), 129.1 (s, Ph), 130.3 (s, Ph), 130.6
(t, JPC ¼ 6 Hz, Ph), 140.3 (t, JPC ¼ 20 Hz, Ph), 215.3 (t, JPC ¼ 5 Hz, CO),
220.9 (s, CO); 31P{1H} NMR (121.5 MHz, C6D6):
d
¼ 98.6(s). Anal.
Calcd for C32H18Cr2FeO10P2: C, 49.01; H, 2.31. Found: C, 48.94; H,
2.32.
4.12. X-ray crystallography
Crystals for X-ray diffraction analysis were grown by storing
a THF solution of 10a, 11, and 12 at ꢁ30 ꢀC. Measurements were
conducted using a Mac Science DIP2030 imaging-plate-based
diffractometer at ꢁ73 ꢀC. The structures were solved by the direct
method and expanded using Fourier techniques. Non-hydrogen
atoms were refined anisotropically, while hydrogen atoms were
located at ideal positions and refined isotropically. All calculations
were performed using the SHELXL-97 crystallographic software
package [32]. A summary of the data collection and structure
refinement details is provided in Table 3.
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Acknowledgments
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2301e2307;
This work was supported by Grants-in-Aid for Scientific
Research Nos. 22550061 and 23105533 from the Ministry of
Education, Culture, Sports, Science and Technology, Japan.
Measurements for the microanalysis and HRMS were made using
PerkineElmer CHNS 2400II and Thermo Fisher Scientific LTQ
Orbitrap XL, respectively, at the Natural Science Center for Basic
Research and Development (N-BARD), Hiroshima University.
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